Author: Robert Hyatt
Date: 15:14:23 09/30/04
Go up one level in this thread
On September 30, 2004 at 15:58:34, Stuart Cracraft wrote: >On September 30, 2004 at 12:06:53, Robert Hyatt wrote: > >>On September 30, 2004 at 05:00:31, Uri Blass wrote: >> >>>On September 30, 2004 at 04:52:12, martin fierz wrote: >>> >>>>On September 30, 2004 at 00:46:26, Uri Blass wrote: >>>> >>>>>On September 29, 2004 at 23:52:15, Stuart Cracraft wrote: >>>>> >>>>>>[D] 4r1k1/p1qr1p2/2pb1Bp1/1p5p/3P1n1R/1B3P2/PP3PK1/2Q4R w - - bm Qxf4; >>>>>> >>>>>>In this position I had everything turned on and got the solution >>>>>>in a little more than 1 1/2 minutes: >>>>>> >>>>>> 1/11 g2f1 0.01 -953 945 g2f1 f4d5 >>>>>> g2f1 f4d5 >>>>>> 2/12 g2f1 0.01 -953 1644 >>>>>> g2f1 f4d5 c1g5 >>>>>> 3/12 g2f1 0.02 -953 5064 >>>>>> g2f1 f4d5 c1g5 d5f6 >>>>>> 4/20 g2f1 0.09 -953 20655 >>>>>> g2f1 f4d5 b3d5 c6d5 c1c7 d6c7 f1g1 >>>>>> 5/22 g2f1 0.65 -953 168943 >>>>>> g2f1 b5b4 b3a4 f4d5 f6g5 d5e7 >>>>>> 6/26 g2f1 2.59 -953 620310 >>>>>> g2f1 b5b4 mtmt >>>>>> 7/32> g2f1 60.58 -552 14192153 g2f1 e8c8 c1b1 f4d5 b1e4 d6b4 f6e5 c7b6 >>>>>> g2f1 e8c8 c1b1 f4d5 b1e4 d6b4 >>>>>> 7/34 c1f4 99.42 5113 24537823 c1f4 e8e6 f4g5 d7e7 b3e6 e7e6 h1d1 d6e7 f6e7 >>>>>> c1f4 e8e6 f4g5 d7e7 b3e6 e7e6 h1d1 >>>>>> >>>>>> >>>>>>I turned off null move (R=2) and got the solution in about 11 seconds: >>>>>> >>>>>>Alpha=-1332 Beta=-531 Maxdepth=9999999 MaxTime=99999999 >>>>>> 1/11 g2f1 0.01 -953 908 g2f1 f4d5 >>>>>> g2f1 f4d5 >>>>>> 2/12 g2f1 0.01 -953 1565 >>>>>> g2f1 f4d5 c1g5 >>>>>> 3/14 g2f1 0.07 -953 20084 >>>>>> g2f1 f4d5 c1g5 d5f6 >>>>>> 4/22 g2f1 0.60 -953 131543 >>>>>> g2f1 f4d5 b3d5 c6d5 c1c7 d6c7 f1g1 >>>>>> 5/26>g2f1 6.80 -552 1607444 >>>>>> g2f1 b5b4 b3a4 f4d5 f6g5 d5e7 >>>>>> 5/36 c1f4 10.70 2260 2466497 c1f4 d6f4 h4h5 g6h5 h1h5 f4h6 h5h6 c7g3 g2g3 d7d6 >>>>>> >>>>>> c1f4 d6f4 h4h5 g6h5 h1h5 f4h6 h5h6 c7g3 g2g3 d7d >>>>>> >>>>>>So now my question is, would it make sense to consider an idea of >>>>>>disabling null move under additional circumstances if those >>>>>>circumstances can be identified. >>>>>> >>>>>> endgame >>>>>> side to move in check >>>>>> inside principal variation >>>>>> last move a null move >>>>>> >>>>>>These are the ones I disable for -- I don't disable null move for >>>>>>any material-related or alpha/beta related measures but perhaps >>>>>>I should. Are any in common use? >>>>>> >>>>>>Stuart >>>>> >>>>>It is better to disable your recapture extensions. >>>>>The problem here is not null move pruning and null move pruning willnot change >>>>>the depth that you solve the problem when you will implement correctly checks in >>>>>the qsearch. >>>>> >>>>>The target of chess programs is not to solve 141 faster but to play better. >>>>>I am almost sure that if only the recapture extension save you many plies in 141 >>>>>then you implement it in a way that is counter productive for games. >>>>> >>>>> >>>>>I wonder how do you get depth 5 without null move pruning >>>>> >>>>>Can you post the remaining depth after every move in the line >>>>>1.Qxf4 Bxf4 2.Rxh5 gxh5 3.Rxh5 Bh6 4.Rxh6 Rd6 Rh8# >>>>> >>>>>There are no checks in this line except the mate and you do checks in the >>>>>qsearch so without recapture extensions you need at least 9 plies for it(after 8 >>>>>plies you enter qsearch after Rd6 and do not find the move Rh8 mate. >>>>> >>>>>If recapture extensions lead to 4 plies extension then it seems clear that your >>>>>new program will be clearly weaker in games. >>>>> >>>>>I suspect that you extend 4 plies in this line because you extend 1 ply every >>>>>time that the last 2 moves are captures. >>>>> >>>>>It is clearly a bad idea to do it and it is clear that even with more reasonable >>>>>restriction of the recapture extension it is not productive for a lot of >>>>>programs. >>>>> >>>>>I suggest that you test the version with the recapture extension in games >>>>>against the version without the recapture extension if you do not believe me >>>>>that your recapture extension is a bad idea. >>>>> >>>>> >>>>>Uri >>>> >>>>hi uri, >>>> >>>>where do you see recapture extensions influencing WAC.141? the main line has no >>>>single "recapture" if you define it as "capture of a piece of the same value, on >>>>the same square, on two successive plies". i think that is the normal definition >>>>of recapture. >>>> >>>>what am i missing? >>>> >>>>cheers >>>> martin >>> >>>It seems that >>>Stuart Cracraft defines it as 2 consecutive captures. >>> >>>He probably extend the line that I showed by 4 plies for that reason: >>> >>>1.Qxf4 Bxf4 =>extension >>>1...Bxf4 2.Rxh5=>extension >>>2.Rxh5 gxh5=>extension >>>2...gxh5 3.Rxh5=>extension >>> >>>I tried to understand how can he get Wac141 at depth 5 without null move pruning >>>when he is using no checks in the qsearch and no mate threat extensions and this >>>was my conclusion and based on his response I understand that my conclusion was >>>correct. >>> >>>Uri >> >> >>If he really does that (IE N consecutive captures triggers N-1 extensions) it is >>broken and will hurt performance no matter what due to over-extending on >>sequences of captures, which results in drastically reduced search depth on >>other lines. > >I thought I was supposed to extend on a recapture because it is obvious! > >How would you (Uri and Bob) extend for this sequence? > >>>1.Qxf4 Bxf4 =>extension >>>1...Bxf4 2.Rxh5=>extension >>>2.Rxh5 gxh5=>extension >>>2...gxh5 3.Rxh5=>extension I am not sure I would extend _any_ of those. The idea behind the recapture extension is to prevent a simple capture from being used to hide a threat that can be pushed over the horizon and out of sight. I only extend when the capture/recapture are equal pieces. IE Qxf4 Bxf4 is not a simple recapture, as the material score changes. My requirements for recapture are (a) two consecutive captures on the same square; (b) the first capture and the second capture are "even trades" such as BxN NxB, or RxR QxR, or PxP NxP, etc. the Qf4 move can't start a recapture sequence since BxQ is not an equal trade, black wins material. (c) I didn't trigger the recapture extension at the previous ply which avoids over-extending on a series such as BxN BxB NxB NxN. I only want _two_ extensions there, not three...
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